@article{MTMT:34596731,
	title = {Three-photon and four-photon absorption in lithium niobate measured by the Z-scan technique},
	url = {https://m2.mtmt.hu/api/publication/34596731},
	author = {Benabdelghani, Imene and Tóth, György and Krizsán, Gergő and Bazsó, Gábor and Szaller, Zsuzsanna and Mbithi, Nelson and Rácz, Péter and Dombi, Péter and Polónyi, Gyula and Hebling, János},
	doi = {10.1364/OE.505995},
	journal-iso = {OPT EXPRESS},
	journal = {OPTICS EXPRESS},
	volume = {32},
	unique-id = {34596731},
	issn = {1094-4087},
	abstract = {Open-aperture Z-scan measurements have been carried out to investigate the three-photon (3 PA) and four-photon absorption (4 PA) coefficients at 800 nm and 1030 nm wavelengths, respectively in congruent and stoichiometric lithium niobate (cLN, sLN) with different concentrations of Mg doping. The laser pulse duration at the two wavelengths were 40 and 190 fs. The peak intensity inside the crystals varied between approximately 110 and 550 GW/cm 2 . The 3 PA and 4 PA coefficients were evaluated using a theoretical model and the results suggest that their minima are at or around the Mg doping level corresponding to the threshold for suppressing photo-refraction for both cLN and sLN. This result can be attributed to the contribution of crystal defects to the 3 PA and 4 PA processes. Furthermore, the 4 PA at 1030 nm exhibited greater nonlinear absorption than the 3 PA at 800 nm under the same intensity level. Possible reasons for this unexpected behavior are discussed. Overall, comparing the 3 PA and 4 PA values of these crystals will enable for selection of the optimum composition of LN crystal for efficient THz generation and for other nonlinear optical processes requiring high pump intensities.},
	year = {2024},
	pages = {7030-7043},
	orcid-numbers = {Rácz, Péter/0000-0001-5099-1031; Dombi, Péter/0000-0002-0736-3512}
}

@article{MTMT:34494015,
	title = {Possibility of CO2 laser-pumped multi-millijoule-level ultrafast pulse terahertz sources},
	url = {https://m2.mtmt.hu/api/publication/34494015},
	author = {Tóth, György and Illés, Gergő and Nazymbekov, Gabit and Mbithi, Nelson and Almási, Gábor and Hebling, János},
	doi = {10.1038/s41598-023-51139-4},
	journal-iso = {SCI REP},
	journal = {SCIENTIFIC REPORTS},
	volume = {14},
	unique-id = {34494015},
	issn = {2045-2322},
	abstract = {In the last decade, intense research has been witnessed on developing compact, terahertz (THz) driven electron accelerators, producing electrons with a sub-MeV—few tens of MeV energy. Such economical devices could be used in scientific and material research and medical treatments. However, until now, the extremely high-energy THz pulses needed by the THz counterparts of the microwave accelerators were generated by optical rectification (OR) of ultrafast Ti:sapphire or Yb laser pulses. These lasers, however, are not very effective. Because of this, we use numerical simulations to investigate the possibility of generating high-energy THz pulses by the OR of pulses produced by CO2 lasers, which can have high plug-in efficiency. The results obtained supposing optical rectification (OR) in GaAs demonstrate that consideration of the self-phase-modulation (SPM) and the second-harmonic-generation (SHG) processes is indispensable in the design of CO2 laser-based THz sources. More interestingly, although these two processes hinder achieving high laser-to-THz conversion efficiency, they can still surpass the 1.5% value, ensuring high system efficiency and making the CO2 laser OR system a promising THz source. Our finding also has important implications for other middle-infrared laser-pumped OR-based THz sources.},
	year = {2024},
	eissn = {2045-2322}
}

@inproceedings{MTMT:34431249,
	title = {Possibility of CO2 Laser Pumped Terahertz Sources},
	url = {https://m2.mtmt.hu/api/publication/34431249},
	author = {Illés, G. and Nazymbekov, G. and Almási, Gábor and Tóth, György and Hebling, János},
	booktitle = {2023 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)},
	doi = {10.1109/CLEO/EUROPE-EQEC57999.2023.10232626},
	unique-id = {34431249},
	year = {2023}
}

@inproceedings{MTMT:34417852,
	title = {Investigation of Terahertz Pulse Generation in Semiconductors Pumped at Long Infrared Wavelengths},
	url = {https://m2.mtmt.hu/api/publication/34417852},
	author = {Polónyi, Gyula and Tóth, György and Mbithi, Nelson and Tibai, Zoltán and Benabdelghani, Imene and Nasi, Luis and Krizsán, Gergő and G., Illés and Hebling, János},
	booktitle = {2023 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)},
	doi = {10.1109/CLEO/EUROPE-EQEC57999.2023.10231383},
	unique-id = {34417852},
	abstract = {Recently, there has been a surge in developing highly efficient, scalable, and compact THz sources with high pumping energy for research in particular in biology, medicine, or particle acceleration. Among various approaches, THz generation by optical rectification (OR) provides an effective and tabletop solution for THz pulses flexibly tailored to the mentioned needs. Up to now, high energy in the low frequency THz regime was reached in LN (1.4 mJ) [1], and in the DSTMS organic crystal (0.9 mJ) [2]. While the former suffers several significant limitations which reduce the efficiency below 1%, the latter has, as all organic nonlinear crystals do, a low damage threshold, hindering its practical use. ZnTe has already been proven to be an efficient source when the low-order multiphoton absorption is suppressed [3], and shows that semiconductors can potentially be good candidates for efficient, high-energy THz sources when pumped at longer wavelength. © 2023 IEEE.},
	keywords = {ENERGY; wide band gap semiconductors; Optical pumping; THz pulse; THz generation; Optical rectifications; Particle acceleration; Terahertz waves; Tellurium compounds; Infrared wavelengths; II-VI semiconductors; Terahertz pulse generation; THz sources; Long infrared; Pumping energies},
	year = {2023},
	orcid-numbers = {Tibai, Zoltán/0000-0002-3196-7586}
}

@article{MTMT:34412825,
	title = {Egyenlőtlenségek a magyarországi fiatal kutatók között: tanulságok a Fiatal Kutatók Akadémiájának 2021-es felméréséből},
	url = {https://m2.mtmt.hu/api/publication/34412825},
	author = {Németh, Brigitta and Munkácsy, B and Vida, Zsófia Viktória and Fröhlich, Georgina and Hatvani, István Gábor and Tóth, György and Solymosi, Katalin and Máté, Ágnes and Lőrincz, László and Lengyel, Balázs},
	doi = {10.1556/2065.184.2023.12.10},
	journal-iso = {MAGYAR TUDOMÁNY},
	journal = {MAGYAR TUDOMÁNY},
	volume = {184},
	unique-id = {34412825},
	issn = {0025-0325},
	year = {2023},
	eissn = {1588-1245},
	pages = {1529-1543},
	orcid-numbers = {Németh, Brigitta/0009-0000-3933-3193; Fröhlich, Georgina/0000-0001-6428-6536; Hatvani, István Gábor/0000-0002-9262-7315; Solymosi, Katalin/0000-0001-5246-2547}
}

@inproceedings{MTMT:34326678,
	title = {Demonstration of The Imaging-Free Wedged Nonlinear Echelon Slab Terahertz Pulse Source},
	url = {https://m2.mtmt.hu/api/publication/34326678},
	author = {Krizsán, Gergő and Polónyi, Gyula and Kroh, T. and Tóth, György and Tibai, Zoltán and Matlis, N.H. and Almási, Gábor and Kärtner, F.X. and Hebling, János},
	booktitle = {2023 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)},
	doi = {10.1109/CLEO/EUROPE-EQEC57999.2023.10231742},
	unique-id = {34326678},
	abstract = {Terahertz (THz) pulse applications such as strong-field control of matter, charged particle manipulation, and acceleration require the highest possible field strengths. To achieve that, high pulse energy and excellent focusability are essential. Conventional tilted-pulse-front setups using lithium niobate (LN) prisms have provided the highest terahertz pulse energies in the low-frequency part of the THz spectrum. However, the scalability of such setups is limited by the following effects: (i) limited interaction length due to angular dispersion, (ii) imaging errors and pulse duration lengthening at the sides of a large pump beam and (iii) prism shape of the LN crystal with large (~63°) wedge angle. Our group proposed several new setups in the past few years to reduce or even eliminate these limitations. Here, we present the result from the first demonstration of the imaging-free wedged nonlinear echelon slab (wedged NLES) [1]. This setup addresses the limitations of conventional tilted-pulse-front setups by reducing (i), eliminating (ii), and dramatically reducing (iii). © 2023 IEEE.},
	keywords = {Charged particles; Niobium compounds; Terahertz pulse; Field strengths; Optical pumping; Particle acceleration; Terahertz waves; Prisms; strong field; Pulse sources; Particle manipulation; High pulse energy; Pulse front; Focusability; Field-control},
	year = {2023},
	orcid-numbers = {Tibai, Zoltán/0000-0002-3196-7586}
}

@article{MTMT:34213706,
	title = {Tilted pulse front pumping techniques for efficient terahertz pulse generation},
	url = {https://m2.mtmt.hu/api/publication/34213706},
	author = {Tóth, György and Polónyi, Gyula and Hebling, János},
	doi = {10.1038/s41377-023-01293-1},
	journal-iso = {LIGHT-SCI APPL},
	journal = {LIGHT-SCIENCE & APPLICATIONS},
	volume = {12},
	unique-id = {34213706},
	issn = {2095-5545},
	abstract = {Optical rectification of femtosecond laser pulses has emerged as the dominant technique for generating single- and few-cycle terahertz (THz) pulses. The advent of the tilted pulse front pumping (TPFP) velocity matching technique, proposed and implemented two decades ago, has ushered in significant advancements of these THz sources, which are pivotal in the realm of THz pump-probe and material control experiments, which need THz pulses with microjoule energies and several hundred kV/cm electric field strengths. Furthermore, these THz sources are poised to play a crucial role in the realization of THz-driven particle accelerators, necessitating millijoule-level pulses with tens of MV/cm electric field strengths. TPFP has enabled the efficient velocity matching in lithium niobate crystals renowned for their extraordinary high nonlinear coefficient. Moreover, its adaptation to semiconductor THz sources has resulted in a two-hundred-times enhancement in conversion efficiency. In this comprehensive review, we present the seminal achievements of the past two decades. We expound on the conventional TPFP setup, delineate its scaling limits, and elucidate the novel generation TPFP configurations proposed to surmount these constraints, accompanied by their preliminary outcomes. Additionally, we provide an in-depth analysis of the THz absorption, refractive index, and nonlinear coefficient spectra of lithium niobate and widely used semiconductors employed as THz generators, which dictate their suitability as THz sources. We underscore the far-reaching advantages of tilted pulse front pumping, not only for LN and semiconductor-based THz sources but also for selected organic crystal-based sources and Yb-laser-pumped GaP sources, previously regarded as velocity-matched in the literature.},
	year = {2023},
	eissn = {2047-7538}
}

@{MTMT:34167389,
	title = {Three-photon and Four-photon Absorption in Lithium Niobate and Lithium Tantalate by Z-scan Technique},
	url = {https://m2.mtmt.hu/api/publication/34167389},
	author = {Benabdelghani, Imene and Tóth, György and Krizsán, Gergő and Mbithi, Nelson and Bazsó, Gábor and Rácz, Péter and Dombi, Péter and Hebling, János and Polónyi, Gyula},
	booktitle = {2023 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)},
	doi = {10.1109/CLEO/Europe-EQEC57999.2023.10232756},
	unique-id = {34167389},
	year = {2023},
	orcid-numbers = {Rácz, Péter/0000-0001-5099-1031; Dombi, Péter/0000-0002-0736-3512}
}

@article{MTMT:34064286,
	title = {Demonstration of an imaging-free terahertz generation setup using segmented tilted-pulse-front excitation},
	url = {https://m2.mtmt.hu/api/publication/34064286},
	author = {Krizsán, Gergő and Polónyi, Gyula and Kroh, Tobias and Tóth, György and Tibai, Zoltán and Matlis, Nicholas H. and Almási, Gábor and Kärtner, Franz X. and Hebling, János},
	doi = {10.1364/OL.493198},
	journal-iso = {OPT LETT},
	journal = {OPTICS LETTERS},
	volume = {48},
	unique-id = {34064286},
	issn = {0146-9592},
	abstract = {A novel, to the best of our knowledge, compact, imaging-free, tilted-pulse-front (TPF) pumped terahertz (THz) source based on a LiNbO 3 slab with a small wedge angle (< 8°) and with an echelon microstructure on its input surface has been demonstrated. Single-cycle pulses of more than 40-µJ energy and 0.28-THz central frequency have been generated by 100-mJ, 400-fs pump pulses with 4.1 × 10 –4 efficiency and excellent focusability. The peak electric field value focused by a single parabolic mirror was 540 kV/cm. Using 200-fs-long pump pulses, the efficiency increased to 1.0 × 10 –3 , which is in qualitative agreement with the measured increased diffraction efficiency in the velocity matched diffraction order. A further ∼8x increase in efficiency is expected by pumping a cryogenically cooled wedged echelon with appropriate step sizes, better microstructured surface quality, and antireflection coating on both the input and the output sides. THz generation efficiency maxima were found at ∼2.7-mm crystal thickness for both pump pulse durations. The focused THz beam was diffraction limited within 5% accuracy. Compared to conventional THz sources, this setup is very compact, easy to align, can be pumped by larger beam sizes maintaining the high THz generation efficiency, and produces THz pulses with superior focusability.},
	year = {2023},
	eissn = {1539-4794},
	pages = {3777-3780},
	orcid-numbers = {Kroh, Tobias/0000-0002-1958-7556; Tibai, Zoltán/0000-0002-3196-7586; Matlis, Nicholas H./0000-0003-2990-3484; Kärtner, Franz X./0000-0001-8829-5461}
}

@book{MTMT:33722561,
	title = {Reflection and/or diffraction-based method and setup to generate high-energy terahertz pulses},
	url = {https://m2.mtmt.hu/api/publication/33722561},
	author = {Hebling, János and Almási, Gábor and Pálfalvi, László and Tóth, György},
	unique-id = {33722561},
	year = {2022}
}